The present invention relates to a flash lamp equipped with a mirror, utilized as a light source for spectroscopy, emission analysis or the like, a stroboscopic light source, a light source for processing high-quality images, or the like.
A conventional technique in such a field is disclosed in Japanese Patent Publication No. HEI 7-120518. In the mirror-equipped f lash lamp described in the above-mentioned publication, a cathode and an anode are disposed facing each other inside a bulb made of glass, the front end of a trigger probe electrode is located between the cathode and the anode, and an inert gas, such as xenon or argon, is encapsulated in the bulb. Further, for attaining high-output light, an ellipsoidal mirror is disposed inside the bulb, and the cathode is inserted in an opening formed in the bottom part of the ellipsoidal mirror, whereby an arc emission point is formed at a first focal point inside the ellipsoidal mirror. By the provision of such an ellipsoidal mirror inside the bulb, a high-output flash lamp is produced.
Due to the above-mentioned configuration, however, the following problem exists in the conventional mirror-equipped flash lamp.
Namely, since the bottom part of the ellipsoidal mirror is formed with an opening, light reflected by the ellipsoidal mirror forms a dark portion in its irradiation area under the influence of the opening, thus lacking uniformity. As a result, when irradiation light is to be introduced into a small-diameter fiber or slit, there have been cases where shortages or inconsistencies in quantity of light occur. While Japanese Patent Publication No. SHO 56-50384 also discloses a xenon lamp equipped with a mirror, the mirror in this case is also formed with an opening for receiving a pedestal for supporting an electrode.
For solving the above-mentioned problem, it is an object of the present invention, in particular, to provide a mirror-equipped flash lamp adapted to generate uniform light whose irradiation inconsistencies are very small.
The mirror-equipped flash lamp in accordance with the present invention is a flash lamp in which an arc emission is generated by cooperation of a cathode, an anode, a trigger probe electrode, and a sparker electrode which are secured by way of stem pins to a stem disposed in an envelope having a light projection window, and this emission is emitted from the light projection window; wherein a mirror structure, contained in the envelope, having a rounded mirror surface facing the light projection window is contained in the envelope between a stem pin for the cathode and a stem pin for the anode and is secured to a leg rising from the stem, the mirror structure and an exhaust port of an exhaust pipe secured to a center of the stem are separated from each other, and an arc emission part is disposed at a focal position of the rounded mirror surface.
In this mirror-equipped flash lamp, when a predetermined voltage is applied between the cathode and the anode, and a trigger voltage is applied to the trigger probe electrode and the sparker electrode, a discharge occurs at the trigger probe electrode and, along with this discharge, a main discharge of an arc occurs between the cathode and the anode. The resulting emission is reflected by the mirror surface, so as to be emitted from the light projection window. Since such a mirror surface is formed as a rounded mirror surface, and a mirror structure is contained between a stem pin for the cathode and a stem pin for the anode, it is not necessary to bore a hole in the rounded mirror surface, the whole mirror surface can be used effectively as a reflecting surface, the reflection characteristics inherent in the mirror surface can fully be utilized, and the arc emission part can be placed at the focal position of the rounded mirror surface while preventing the stem pins from penetrating through the rounded mirror surface. Also, since the exhaust port of the exhaust pipe and the mirror structure are separated from each other, the exhaust port of the exhaust pipe facing inside the envelope would not be closed by the mirror structure.
Preferably, in this case, the mirror structure comprises a mirror portion made of glass having the rounded mirror surface, and a mirror holder surrounding the mirror portion. When such a configuration is employed, in the forming of the rounded mirror surface, the surface processing is easier than that in metals such as aluminum, thereby yielding a surface which not only can be made at a lower manufacturing cost but also has a low surface roughness and high surface precision. Also, when aluminum is vapor-deposited on a glass surface to form a rounded mirror -surface, a firm specular surface would be formed on the glass surface, whereby a highly durable rounded mirror surface can be obtained.